One conventional bearing assembly includes inner and outer races between which are positioned a plurality of circumferentially spaced bearings, or bearing elements such as ball bearings, which are circumferentially spaced apart by an annular cage. The outer race is fixedly joined to a stationary housing, and the inner race is fixedly mounted to a rotor shaft which is supported thereby.
For high rotational speed applications of the bearing assembly, for example at DN values on the order of about 1.5.times.10.sup.6, the inner race is axially split for providing a radially extending center plane disposed generally in line with the bearing centers, with a plurality of circumferentially spaced and radially extending oil center feed passages disposed at the split line. The center feed passages effectively carry lubricating oil radially outwardly to the bearings under centrifugal force upon rotation of the inner race and shaft. In a high speed split inner race bearing assembly, the inner races are subjected to relatively high stress induced by rotation. In particular, the central zone over which the ball tracks is most sensitive to any additional stress risers caused by material discontinuities such as holes or slots which can decrease the effective life of the bearing assembly.
Furthermore, conventional split inner race bearing assemblies may also include secondary radial passages for lubricating adjacent components of the bearing assembly spaced axially from the split line. Since the lubricating oil channeled through both the center and secondary passages is typically provided from a common oil source, suitable means must be provided for ensuring desired splits of the oil between the center and secondary passages. For example, means must be provided to ensure that the supply oil is not primarily channeled radially upwardly through one of the center or secondary passages by centrifugal force before reaching the other of the passages. The prior art recognizes this particular problem and offers solutions thereto of varying complexity and effectiveness. In one prior art design, it is recognized that oil split between center and secondary passages is proportional to rotational speed of the shaft, as well as angular alignment between the two inner race halves. In other designs, a more constant oil split between the center and secondary passages is obtained irrespective of rotational speed but with increased complexity and undesirable stress increasing passages adjacent to the split line which are undesirable for high speed operation.